1. Field of the Invention
This invention relates to a freight moving apparatus to be mounted in a trackless carrier vehicle for moving a freight or an article of freight from a predetermined position in the carrier vehicle to a predetermined position in a freight station in a factory or a warehouse and vice versa.
2. Description of the Related Art
There are currently known various kinds of freight moving apparatuses to be mounted in a carrier vehicle for automatically loading and unloading the freight at the predetermined positions.
To control the loading and unloading, a limit switch in the form of an actuator or a photoelectric transducer is customarily used as a detector. This limit switch detects whether the freight arrives at a predetermined position in the carrier vehicle or freight station where the freight is to be placed, in an attempt to stop the freight at the predetermined position upon such detection.
With this limit switch, however, partly since it would practically take a time to activate a drive source of the freight moving apparatus after the detection, and partly since the moment of inertia would be exerted on the freight moving apparatus while the freight is moving, it is difficult to stop the freight at the predetermined position so that the freight would be stop at staggered positions.
Consequently if the freight is not located in the predetermined position in the freight station in particularly, various troubles would occur in moving the freight to a station for a subsequent step of production by the carrier vehicle. For example, the freight moving apparatus would occasionally not reach the freight in the station so that the freight cannot be loaded on the carrier vehicle.
Further if the stroke of the freight moving apparatus can be controlled only from the trackless carrier vehicle, the carrier vehicle itself would tend to move in a staggering manner. Even though an attempt is made to move the carrier vehicle to the predetermined position and to stop there, the carrier vehicle would actually tend to be stopped considerably short of the predetermined position in the freight station so that the freight loaded on the carrier vehicle cannot be placed exactly at the predetermined position in the station, thus causing a trouble that the freight would be placed off the station.